Electrically heated screen construction



March 15, 1955 T. w; HANNON ELECTRICALLY HEATED SCREEN CONSTRUCTION 2 Sheets-Sheet 1 Filed June 4, 1952 I INVENTOR.

. War/ms WHannon ATTORNEYS March 15, 1955 w HANNQN ELECTRICALLY HEATED SCREEN CONSTRUCTION Filed June 4, 1952 2 Sheets-Sheet 2 INVENTOR.

' Th 077 203 WHannon ATTORNEYS United States Patent ELECTRICALLY HEATED SCREEN. CONSTRUCTION Thomas W. Harmon, Canton, Ohio Application June 4, 1952, Serial No. 291,683

11 Claims. (Cl. 209-238) The invention relates generally to electrically heated screens made of conducting material, and more particularly to electrically heated screens used for the industrial screening of materials. When motion is imparted to such screens, there are two principal types known as vibrating screens, and hummer screens. In a vibrating screen, the frame mounting the screen is oscillated. In a hummer screen, the frame mounting is stationary, and motion is imparted to the screen itself as a diaphragm by a rapidly reciprocating armature connected to the screen and operated by an alternating current solenoid coil.

When screens used for industrial screening of materials are electrically heated, much less blinding or clogging of the screens takes place than when operated without electrical heating. The electrical heating of such screens is desirable in many existing industrial material screen installations which have previously been operated without electrical heating, and which it is desired to equip with electrically heated screens, with a minimum change in other parts of the installation.

In my prior application for United States Letters Patent, Serial No. 266,378, filed January 14, 1952, there is set forth electrically heated screen construction embodied in a vibrating screen. Prior to the construction set forth in said application, conventional electrically heated screens have included copper conductor or bus bars bolted to the top of the screen cloth along the sides thereof, with backup bars on the bottom side of the cloth, and conductor and conductor cables attached to the conductor bars for supplying current thereto. For efficient heating, the copper cables must be connected to the conductor bars at relatively short intervals, so that for a long screen the cables would be connected to both ends of the conductor bars as well as to the central portions.

The principal objection to this conventional construction is the large amount of labor involved in replacing the screen cloth when worn and disconnecting and reattaching the conductor bars to the new cloth. This operation involves removing and reconnecting a large number of bolts for attaching the conductor bars to the screen cloth, and also disconnecting and reattaching the several copper cables carrying current to the copper conductor bars.

Another objection to this conventional construction is that all of the conductor cables as well as the conductor bars are above the screen where they are subjected to the constant abrasion of the material passing over and through the screen. Moreover, where a multi-deck screen is used having two or more decks of screen cloth, the bottom deck is the one most desirably heated, but it is not practical to support the required large quantity of cables between the bottom deck and an upper deck because of the limited amount of space available.

In certain prior constructions it has been attempted to overcome some of the foregoing difficulties by making the skirt boards which clamp the sides of the screen cloth of copper to act as conductor or bus bars, and connecting the conductor cables to one end of the bars. Such a construction is very expensive, because the special shape of the skirt board has a relatively thick cross section, and being made entirely of copper, the overall weight of the copper skirt board is relatively great. A foot section may weigh as much as 400 pounds.

Moreover, a uniform temperature cannot be maintained throughout the screen cloth because of the voltage drop from the end connected with the conductor cables to the other end. This extremely heavy weight makes the copper skirt board difiicult to handle when screen replacements are required. Moreover this type of all copper skirt board is subject to abrasion by material passing over the top of the screen, and where extremely abrasive material is being screened, such as coke breeze or slag, these all copper skirt boards wear out in a short time. It is also necessary where the bottom deck of a double deck screen unit is to be electrically heated, that the copper cable connections be bolted to the all copper skirt board at one end or the other of the screen assembly. In such an assembly, 6 feet wide and 16 feet long, it is necessary that the skirt board he made in lengths of 4 feet, and a copper jumper bolted between the joining lengths, so that the current will pass from one end of the screen to the other. Because of this arrangement, each time screen cloths are changed, it is necessary for the screen maintenance man to crawl between the two decks of the screen assembly and unbolt these skirt board bus bar connections so that the skirt boards may be lifted up out of the way.

In certain other prior constructions, it has been attempted to overcome some of the foregoing difiiculties by a construction including a copper angle running the entire length of the inside of each side plate of the screen assembly. A steel skirt board is tensioned against this copper angle at the top and the hook strip of the screen cloth at the bottom. There are two main difiiculties with this type of installation. First, the current must pass through the steel skirt board before entering the screen cloth, which results in a power loss because the skirt board offers resistance to the flow of the current and heating takes place within the steel skirt board. Second, a poor contact point exists at the top of the skirt board where it rests against the copper angle bar.

The objects of the present invention include generally the provision of a new and improved electrically heated screen construction which is adapted for use in many different types of installations, and which is particularly adapted for use in installations where motion is imparted to the screen, and which overcomes objectionable features of prior constructions.

More particularly, the objects of the present invention include the provision of such a new and improved electrically heated screen construction which is specifically adapted for use either as original equipment in hummer screens, or as quick change attachments for existing hummer screens.

More specifically, a further object of the present invention is to provide such a new and improved electrically heated screen construction in which the screen cloth is quickly and easily replaced, without disconnecting the current-conducting bars which contact the screen cloth.

Another object of the present invention is to provide such a new and improved electrically heated screen construction in which the conductors are substantially protected from the abrasion of the material being screened, and with minimum insulation required around the conductor bars.

A further object of the present invention is to provide such a new and improved electrically heated screen construction having a simplified construction and arrangement of parts, permitting economical manufacture and maintenance, and convenience in use.

The foregoing and other objects are attained by the electrically heated screen construction, parts, combinations, and subcombinations, which comprise the present invention or discovery, and the nature of which is set forth in the following general statement, and preferred embodiments of which are set forth in the following description, and which are particularly and distinctly pointed out and set forth in the appended claims forming part hereof.

The nature of the present invention, may be stated in general terms as embodying improved electrically heated screen construction including a frame having two longitudinally extending main frame members which are preferably parallel and have webs with opposite inside faces. A composite skirt board extends along the inside face of each frame member web. Each composite skirt board has a web with an upper border portion and a lower border portion, and an outside face opposite the inside face of the adjacent frame member web. Insulated hinge means pivotally connect the upper border portion of each skirt board web with the adjacent frame member. A

' tongue bus bar extends along the outside face of the lower border portion of each skirt board web and is secured thereto. A screen deck extends between the frame members below the skirt board webs and the tongue bus bars. The screen deck has opposite longitudinally extending grooves, each engaged by one of the tongue bus bars. Releasable insulated tension clamp means operate between each skirt board web and the adjacent frame member web, whereby the screen deck may be stretched between the frame members and electric current fed therethrough from the bus bars, or whereby the screen deck may be released from engagement with the tongue bus bars, when it is desired to remove the screen deck from the other parts of the construction.

The improved electrically heated screen deck construction, as above described in general terms, requires a minimum quantity of insulation material.

By way of example, embodiments of the new and improved electrically heated screen construction and component parts of the present invention are illustrated in the accompanying drawings forming part hereof, in which:

Figure 1 is a top plan view of a hummer screen including certain parts of usual construction and other parts which may be either original equipment parts or attachment parts, whereby the improvements of the present invention are incorporated in the illustrated hummer screen.

Fig. 2 is a front end elevation thereof, with portions broken away;

Fig. 3 is an enlarged fragmentary transverse sectional view thereof, as on line 33, Fig. 1;

Fig. 4 is a fragmentary elevational view thereof, looking in the direction of the arrows 44, Fig. 3;

Fig. 5 is a view similar to Fig. 3, showing a modified form of the improved hummer screen of Figs. 1 to 4, inc usive.

Similar numerals refer to similar parts throughout the drawings.

The embodiment of the improved electrically heated screen construction of the present invention illustrated in Figs. 1 to 4, inclusive, constitutes a hummer screen unit indicated generally by 10, and which includes an open ended frame indicated generally by 11, and having laterally spaced longitudinally extending side channels 12a and 12b which are the main supporting members of the unlt.

The channels 12a and 12b, respectively, include top and bottom horizontal flanges 13a and 14a, and 13b and 14b, and vertical webs 15a and 15b. The top and bottom flanges of each channel extend upwardly, and the webs of the channels present smooth opposite inside faces towards each other.

The frame 11, as shown, also'includes a central bridge member 16 having opposite downwardly extending end flanges 17a and 17b secured by bolt and nut sets 18 to the channel webs 15a and 15b, respectively. The bridge end flanges 17a and 17b have outside faces abutting the inside faces of the channel webs 15a and 15b.

An improved composite skirt board 19a extends longitudinally along the inside face of channel web 15a, and a pair of improved insulated hinges each indicated generally by 20 pivotally connect the upper longitudinally extending edge border portion of the web 21a of the skirt board 19a to the upper portion of the channel Web 15a adjacent the top flange 13a.

Similarly, an improved composite skirt board 19b extends longitudinally alongthe inside face of channel web 15b, and a pair of insulated hinges 20 pivotally connect the web 21 of the skirt board 1% to the channel web 15b.

The composite skirt board 19a also includes a longitudinally extending improved bus bar 22a secured to the lower edge border portion of the web 21a on the outside face thereof opposite the inside face of the channel web 15a. The'bus bar 22a has a transversely bevelled crosssection, and constitutes a V-tongue bus bar. Similarly the composite skirt board 19b also includes a longitudinally extending V-tongue bus bar 22b secured to the lower border portion of the web 21b on the outside face thereof opposite the inside face of the channel web 15b. The bus bars 22a and 22b are made of high conductive material, such as copper.

A screen deck 23 of screening made of lower conductive material such as steel or stainless steel wire, extends laterally between the channels 12a and 12b and longitudinally the entire length thereof, and below the composite skirt boards 19a and 19b. On the longitudinal edge border portion of the screen deck 23 adjacent the channel 12a, there is secured a longitudinally extending hook bar 24a having a V cross-section, and constituting a two ply V-groove angle hook bar. One leg of the angle hook bar 24a is horizontal the other leg thereof extends upwardly and laterally away from the channel 12a, and presents its V-groove for engagement by the V-tongue of the bus bar 220, the hook bar being of conducting material such as steel or copper, and the screen deck border portion being formed with a V-groove fitting between the plies of the V-groove of the hook bar.

Similarly, an oppositely opening V-groove angle hook bar 24b is secured to the longitudinal edge V-groove border portion of the screen deck 23 adjacent the channel 1%, the hook bar 24b and screen deck V-groove border portion presenting their V-groove for engagement by the V-tongue of the bus bar 22b.

When the grooves of the screen deck border portions and the hook bars 24a and 24b are engaged by the tongues of the bus bars 22a and 22b, the composite skirt boards 19a and 19]) have tension applied thereto for swinging them about their respective horizontal pivotal connections with the channel webs 15a and 15b. This stretches the screen deck 23 laterally between the side channels 12a and 12b.

Means for applying this tension on the skirt boards 19a and 19b and the screen deck 23 are provided as shown by a plurality of insulated clamp bolt and nut sets 25 for each skirt board. Each insulated clamp bolt and nut set 25 operates between its skirt board and the adjacent channel.

One of the insulated clamp bolt and nut sets 25 is shown in detail in Fig. 3, together with the construction details of associated parts. Referring to this particular insulated clamp bolt and nut set 25, the skirt board web 21a has a circular hole 26 formed therein above the bus bar 22a. The channel web 15a has a larger hole 27 formed therein, at a lower level than the hole 26. An angled thrust plate 28 is secured on the outside of the channel web 15a, and has formed therein a hole 29 opposite the channel web hole 27.

A cylindrical sleeve 30 of insulating material fits in the skirt board web hole 26, and extends from the opposite sides thereof. A washer 31 of insulating material fits on the sleeve 30 on the inside of the skirt board web 21a, the outside face of the washer 31 abutting the inside face of the skirt board web, and the inside end face of the sleeve 30 and the inside face of the washer 31 being flush.

A carriage bolt 32 has a shank 33 extending through the holes 29 and 27, and the bore of the sleeve 30. The head 34 of the carriage bolt is on the outside of and abuts against the thrust plate 28. The threaded inner end 35 of the bolt shank 33 extends bevond the washer 31 on the inside of the skirt board web 21a. A metal washer 36 is located on the shank end 35 against the insulating washer 31, and a nut 37 is screwed on the threaded shank end 35 against the washer 36.

The insulating washer 31 and the insulating sleeve 30 together constitute a shouldered tubular insulator, interposed between the metallic bolt shank 33, and washer 36 and nut 37. Thus the clamping bolt and nut set 25 and the frame 11 are insulated from the skirt board 19a.

One of the improved insulated hinges is illustrated in detail in Figs. 3 and 4, and includes a U-bracket 40 having a web 41 secured to the channel web 15a by a bolt and nut set 42. Laterally spaced legs 43 of the U-bracket 40 extend inwardly from the web 41, and the legs 43 have aligned holes 44 formed therein. A swinging hinge member 45 has lower strap members 46 folded on each other and forming an upper sleeve member 47. The lower strap members 46 are connected to the upper portion of the skirt board web 21a.

An insulating sleeve 48 extends through the strap sleeve member 47 and beyond the ends thereof. An nsulating washer 49 is located on each end of the insulating sleeve 48 beyond the strap sleeve member 47 which is made of steel or other metal. The insulating sleeve 48 and insulating washers 49 thus form a separable insulating spool which mounts the hinge sleeve member 47. This spool is located between the U-bracket legs 43, the bore of the insulating sleeve 48 registering with the U bracket leg holes 44. A cotter pin fastened headed hinge pm 50 has its shank extending through the holes 44 and the bore of the sleeve 48, and thus pivotally mounts the insulating spool on the metal bracket 40, and insulates the metal hinge member 45 and other parts of the skirt board 19a from the frame 11.

Referring to Figs. 1 and 2, a solenoid operated vertically reciprocating armature unit indicated generally by 51 18 mounted on the bridge member 16 centrally of its span. The armature unit 51 is of usual construction and operation in hummer screen units, and includes the vertically reciprocating armature 52 having an insulated connection 53 with the center of the screen deck 23. Preferably there are longitudinally extending upper and lower remforcing strips 54 included in the connection of the armature 52 with the screen deck 23.

At one end of the bus bar 22a, conductor leads 55a connect the bus bar 22a with one terminal of an electric heater unit, not shown. At the other end of the bus bar 22b, conductor leads 55b connect the bus bar 22b with the other terminal of the heater unit. The heater unit may be of usual or special transformer construction adapted to deliver low voltage and high amperage alternating current to the bus bars 22a and 2212, thereby heating the high resistance screen deck 23 connected therebetween.

When it is desired to change a worn out screen deck 23, it is only necessary to loosen the clamp bolt and nut sets 25 sufliciently to swing the V-tongue bus bars 22a and 22b out of engagement with the V-groove hook bars 24a and 24b of the screen deck 23. The armature 52 is disconnected from the screen deck 23, and the worn out screen deck may be removed, and a new one installed by reverse operations.

The conductor leads 55a and 55b are not required to be disconnected during changing of the screens.

It is apparent that the composite skir-t boards 19a and 19b and other parts of the improved electrically heated screen construction of the present invention may be easily and quickly assembled with the frame 11 and the armature 52, either as original equipment or as a quick change attachment.

The improved electrically heated screen construction, as above described, attains the stated objects of the invention.

In Fig. 5, there is shown a modified embodiment of the invention in the form of a hummer screen unit 110 which is generally similar to the unit 10, with the exception that the unit 110 includes bus bars having a different transverse cross-section than the bus bars of the unit 10. In Fig. 5, the bus bar 122a is shown, and it has a rounded tongue cross-section, and fits into a rounded groove border portion of the screen deck 123, which in turn fits into a rounded groove formed in the hook bar 124a.

Moreover, in the unit 110, a shelf angle 160 is secured on the inside of the channel web 115a below the hook bar 124a. An insulation strip 161 is interposed between the shelf leg of the angle 160 and the hook bar 124a, and similarly an insulation strip 162 is interposed between the inside face of the channel web 115a and the hook bar 124a.

In the foregoing description, certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such words are used for descriptive purposes herein and are intended to be broadly construed.

Moreover, the embodiments of the improved construction illustrated and described herein are by way of example, and the scope of the present invention is not limited to the exact details of construction.

Having now described the invention, the construction, the operation and use of preferred embodiments thereof, and the advantageous new and useful results obtained mechanical equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.

I claim: 4

1. Electrically heated screen construction including a frame having two laterally spaced longitudinally extending side members, each frame side member having an inside face opposite the inside face of the other frame side member, a composite skirt board extending along the inside face of each frame side member, each composite skirt board including a web with an upper border portion and a lower border portion and an outside face opposite the inside face of the adjacent frame member, insulated hinge means pivotally connecting the upper border portion of each skirt board web with the adjacent frame member, a tongue bus bar secured to and extending along the outside face of the lower border portion of each skirt board web, a screen deck extending between the frame side members below the tongue bus bars and the skirt board webs, the screen deck having opposite longitudinally extending formed border portions, each formed border portion constituting a longitudinally extending groove, the opposite tongue bus bars engaging the opposite screen deck grooves, and releasable insulated tension clamp means connecting each skirt board web and its mounting frame side member, whereby applying tension clamping pressure to the composite skirt boards towards their mounting frame side members serves to stretch the screen deck, and whereby releasing the clamping pressure permits removal of the screen deck from the tongue bus bars, and the space immediately below the screen deck being clear of frame members to permit rapid removal of the screen deck.

2. Electrically heated screen construction as set forth in claim 1, and in which the frame side members are parallel with each other.

3. Electrically heated screen construction as set forth in claim 1, and in which each frame side member has a web having the inside face, and the insulated hinge means pivotally connects the associated skirt board web with the frame side member web.

4. Electrically heated screen construction as set forth in claim 1, and in which each tongue bus bar has a V cross-section, and each screen deck formed border portion groove has a V cross-section sized to fit its engaged V tongue bus bar.

5. Electrically heated screen construction as set forth in claim 1, and in which each tongue bus bar has an electrical conductivity greater than the electrical conductivity of the screen deck.

6. Electrically heated screen construction as set forth in claim 1, and in which each tongue bus bar has an electrical conductivity greater than the electrical conductivity of the skirt board web mounting the bus bar.

7. Electrically heated screen construction as set forth in claim 6, and in which each tongue bus bar has an electrical conductivity greater than the electrical conductivity of the screen deck. 'j

8. Electrically heated screen construction as set forth in claim 1, and in which the screen deck includes screening extending laterally between the frame side members, the screening having longitudinally extending hook bars secured thereto, and the hook bars constituting at least part of the formed] border portions of the screen deck.

9. Electrically heated screen construction as set forth in claim 1, and in "which the releasable insulated tension clamp means connecting each skirt board web and its mounting frame side member includes a plurality of insulated clamp bolt and nut sets each co-acting between its associated skirt board web and its mounting frame side member.

10. Electrically heated screen construction as set forth in claim 9, and in which for each insulated clamp bolt and nut set, the associated skirt board web has a hole formed therein and the mounting frame side member has a hole formed therein, a tubular insulator engaged in the hole of the skirt board Web, a headed bolt having a shank extending through the web hole and the bore of the tubular sleeve and having its head thrusting against the outside of the frame side member, the inner end of the bolt shank being threaded and extending beyond the inner end of the tubular insulator, and a nut screwed on the threaded end of the bolt shank against the inner end of the tubular insulator.

11. Electrically heated screen construction as set forth thereby; the new and useful constructions, and reasonable 35 in claim 10, and in which the tubular insulator has a 7 8 shoulder on its end inside the skirt board web, and the 2,190,993 Muir Feb. 20, 1940 shoulder abuts the skirt board web and the nut. 2,217,920 Roubal Oct. 15, 1940 References Cited in the file of this patent FPREIGN PATENTS 5 SWltZerland Apr. 16, 1,397,342 Sturtevant Nov. 15, 1921 OTHER REFERENCES 1,642,652 Gobiet Sept. 13, 1927 Thermo-Deck, published by Allis-Chalmers in Bulletin 1,992,629 Oishei et a1 Feb. 26, 1935 O7B7812. Received in Patent Oflice on May 12, 1952. 2,077,678 Delamater Apr. 20, 1937 10 (Copy in Division 55.)

2,090,767 Sayer et a1. Aug. 24, 1937 

